We waited a long time for our DC (Including various cycles of IVF) and had DC1 when I as was almost 43 (IVF fresh cycle, own eggs) and DC2 when I was almost 47 (IVF frozen cycle, own eggs). I am now 60 and they are almost 18 and 14.
Yes, I would prefer to have had them earlier but I do not think that they have suffered from having older parents.
We have been able to do all sorts of things with them that younger parents do with their children. We have been able to give them more financial stability than many younger parents. We are more emotionally mature than many younger parents, and have more life experience to offer them. Having them has kept us younger in outlook as well.
Our situation is a bit different from yours, and there are definitely risks you need to weigh up, plus you need to weigh up the pros and cons for your DC1. I should add that the risks for my DC2 were linked to my age when his embryo was created (ie when I was 42 rather than 47.) And there are the risks of you not being around for them as long as if you had them younger, although if I live to the same age as my own mother is (and she is still hale and hearty, touch wood), DC1 will be 46 and DC2 will be 42, so hopefully pretty established in their lives.
Some of the downsides are: (1) needing to make financial provision (eg taking our hefty life insurance policies) to ensure they would be financially secure if things die go wrong; (2) needing to have someone in the family ready to take them on if we went early; (3) dealing with the demands of aged parents and young children at the same time; (4) knowing that we will need to keep working longer to see them through school and uni etc.
By the way, I agree that the nonsense spouted by some PPs about older mums always being too menopausal to be able to deal with toddlers or being too senile/decrepit by the age of 60 to do anything with their children, etc etc is not universally true. I personally sailed through the menopause, even though I was essentially looking after two young children alone and working at the time (because DH was abroad for long periods) and I still spend a lot of time doing things with my DC. OK, I don't play a lot of football with them now, but how many younger parents do that either?
Weigh everything up, and do what is right for you and your family.